Joined dissimilar materials and method

ABSTRACT

A method of forming a wire includes providing a first wire section comprising a first material and providing a second wire section comprising a second material different from the first material. A joining section is formed having a first end and a second end such that the first end of the joining section comprising a material that is compatible with the first material and such that the second end of the joining section comprising a material that is compatible with the second material. The first wire section is welded to the first end of the joining section and the second wire section is welded to the second end of the joining section. Forming the joining section includes forming the joining section via a process selected from a group comprising electrodeposition, three-dimensional printing, direct typing process, LIGA, lithography and stacking processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/813,847, entitled “JOINED DISSIMILAR MATERIALS AND METHOD,” having afiling date of Jun. 11, 2010, and is incorporated herein by reference.

BACKGROUND

The present invention relates to joined dissimilar materials. In oneembodiment, the joined materials form a guide wire configured forintravascular use. For example, intravascular guidewires are used inconjunction with intravascular devices such as catheters to facilitatenavigation through the vasculature of a patient. Such guidewires aretypically very small in diameter. In some applications, a guidewire canhave multiple sections that are joined together in order to form asingle wire. Joining sections of such a wire having a small diameter canbe challenging, particularly where the sections being joined areconfigured of different materials. Because there are limitations to manypresent approaches, there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate cross-sectional views of joined dissimilarmaterials in accordance with one embodiment.

FIG. 2 illustrates a cross-sectional view of a joining section inaccordance with one embodiment.

FIG. 3 is a table illustrating the material content of layers of ajoining section in accordance with one embodiment.

FIG. 4 illustrates a cross-sectional view of a joining section inaccordance with one embodiment.

FIGS. 5A-5C illustrate forming a joining section in accordance with oneembodiment.

FIG. 6 illustrates a cross-sectional view of a joining section inaccordance with one embodiment.

FIG. 7 illustrates a cross-sectional view of a joining section inaccordance with one embodiment.

FIG. 8 illustrates a perspective partially ghosted view of a joiningsection in accordance with one embodiment.

FIG. 9 illustrates a perspective partially ghosted view of a joiningsection in accordance with one embodiment.

FIG. 10 illustrates a perspective partially ghosted view of a joiningsection in accordance with one embodiment.

FIG. 11 illustrates a perspective partially ghosted view of a joiningsection in accordance with one embodiment.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

FIG. 1A illustrates a guidewire 10 in accordance with one embodiment. Inone embodiment, guidewire 10 has a proximal section 12, a distal section14 and a joining section 16. In one case, proximal, distal and joiningsections 12, 14 and 16 are each configured of separate wire segmentsthat are joined together at joining section 16. In some embodiments,proximal and distal sections 12 and 14 are adapted with differingdiameter regions, are adapted and configured to obtain a transition instiffness, and provide a desired flexibility characteristic. In FIG. 1,guidewire 10 is illustrated with a truncation in its ends, as its lengthmay vary in accordance with particular applications.

As used herein, the proximal section 12 and the distal section 14 cangenerically refer to any two adjacent wire sections along any portion ofguidewire 10. Furthermore, although discussed with specific reference toguidewires, the wire segments can be applicable to almost anyintravascular device. For example, they are applicable to hypotubeshafts for intravascular catheters (e.g., rapid exchange ballooncatheters, stent delivery catheters, etc.) or drive shafts forintravascular rotational devices (atherectomy catheters, IVUS catheters,etc.).

In one example, proximal section 12 can be configured of a relativelystiff material, such as stainless steel wire. Alternatively, proximalsection 12 can be comprised of a metal or metal alloy such as anickel-titanium alloy, nickel-chromium alloy, nickel-chromium-ironalloy, cobalt alloy, or other suitable material. In general, thematerial used to construct proximal section 12 can be selected to berelatively stiff for pushability and torqueability.

Also, in some embodiments, distal section 14 can be configured of arelatively flexible material, such as a super elastic or linear elasticalloy, wire, such as linear elastic nickel-titanium (NiTi), oralternatively, a polymer material, such as a high performance polymer.Alternatively, distal section 14 can be configured of a metal or metalalloy such as stainless steel, nickel-chromium alloy,nickel-chromium-iron alloy, cobalt alloy, or other suitable material. Ingeneral, the material used to configure distal section 14 can beselected to be relatively flexible for trackability.

In one embodiment, guidewire 10 is configured for intravascular use andcan be used in conjunction with intravascular devices such as cathetersto facilitate navigation through the vasculature of a patient. Guidewire10 is configured in a variety of sizes, and in one embodiment, its outerdiameter ranges from about 0.005 to about 0.02 inches.

FIG. 1B illustrates an exploded view of guidewire 10 in accordance withone embodiment. Joining section 16 is made of two different materials.

For example, on a first end 16 a directly adjacent proximal section 12,joining section 16 is made of a material that is compatible with thematerial of which proximal section 12 is made. As such, proximal section12 can be readily and easily welded to first end 16 a of joining section16, because of the compatible materials. Furthermore, on a second end 16b directly adjacent distal section 14, joining section 16 is made of amaterial that is compatible with the material of which distal section 14is made. As such, distal section 14 can be readily and easily welded tosecond end 16 b of joining section 16, because of the compatiblematerials.

In one embodiment, first end 16 a of joining section 16 is stainlesssteel and proximal section 12 is also stainless steel. Also, second end16 b of joining section 16 is nickel-titanium (NiTi) and distal section14 is also nickel-titanium. In this way, first end 16 a is readilyweldable to proximal section 12 and second end 16 b is readily weldableto distal section 14.

In one embodiment, first end 16 a of joining section 16 is a metal ormetal alloy such as nickel-chromium alloy, nickel-chromium-iron alloy,cobalt alloy, or other similar material and proximal section 12 is of ahighly similar material. Also, second end 16 b of joining section 16 ismade of a relatively flexible material, such as a super elastic orlinear elastic alloy, and distal section 14 is of a highly similarmaterial. In this way, first end 16 a is readily weldable to proximalsection 12 and second end 16 b is readily weldable to distal section 14.Forming joining section 16, which is made of two different materials,can be accomplished in a variety of ways consistent with the exemplaryembodiments.

FIG. 2 illustrates one embodiment of joining section 16 formed via layersections. In one embodiment, joining section 16 consists of a pluralityof layer sections, in one example, layers 20-30. In one embodiment, thematerial in each of the layers 20-30 varies from one layer to the next.For example, in one example, layer 20 of joining section 16 is allstainless steel, layer 21 is mostly stainless steel, but also includes asmall amount of nickel-titanium. Each of layers 22-29 then progressivelyincludes increasing amounts of nickel-titanium and decreasing amounts ofstainless steel. Layer 30 is all nickel-titanium. As such, layer 20 isreadily weldable to stainless steel proximal section 12 and layer 30 isreadily weldable to a nickel-titanium distal section 14.

FIG. 3 illustrates the material content, as a percentage, for each ofthe layers of joining section 16 in one example. As such, layer 20 is100% stainless steel and 0% nickel-titanium, layer 21 is 90% stainlesssteel and 10% nickel-titanium, layer 22 is 80% stainless steel and 20%nickel-titanium, layer 23 is 70% stainless steel and 30%nickel-titanium, and so forth, until layer 30, which is 0% stainlesssteel and 100% nickel-titanium.

In other embodiments, more or less layers can be used in order to moregradually or more steeply change the material content of joining section16 from one of its end to the other. In the illustration, 11 layers areshown, but more or fewer layers can be used in accordance with variousembodiments. Also, various other percentages of material changes can beused. In the illustrations, the percentages of material changes from onelayer to the next are shown in increments of 10, but larger or smallerincrements can be used in accordance with various embodiments.

In one embodiment, the layer sections of joining section 16 are formedvia three-dimensional screen printing or Direct Typing Process (DTP).Three-dimensional screen printing, or DTP, is a known process forproducing three-dimensionally shaped objects via a layering process. DTPuses to form a green compact by printing a liquefied metallic powdercomposition onto a substrate, and then repeating layer by layer untilthe green compact is obtained and the compact is sintered to a metal.

In one embodiment, a green compact is formed in order to make joiningsection 16. Initially, a metal-containing paste is mixed and thenpressed through a sieve or mask. In one embodiment, the paste alsocontains an organic binder and a carrier liquid, for example, water. Afirst layer, such as layer 20, is printed by pushing the paste through ascreen with a first print. In the first screen print, themetal-containing paste includes a first metal material and includes noneof a second metal material. The first layer is then allowed to dry. Asecond layer is then printed on the first dried layer. Between theprinting of the first and second layers, however, the composition of thepaste is varied such that the amount of the first metal material isreduced and the amount of the second metal material is increased fromnone.

Each subsequent layer is then printed over the dried previous layer,gradually adjusting the composition of the metal-containing pastebetween each printing such that a gradient progressing from the firstmetal material to the second metal material is produced in the greencompact. Subsequently, the green compact is debindered and sintered,whereby a joining section, such as joining section 16 of FIG. 2, isobtained.

In one embodiment, the individual printed layers of the green compactare on the order of 10-40 μm. As such, in one example, two or morelayers may be printed before the composition of the paste is varied. Inthis way, a gradient progressing from the first metal material to thesecond metal material is still produced in the green compact, but eachlayer illustrated in FIG. 2 may actually represent two or more actualprinted layers.

In one embodiment, the first material in the above-describedthree-dimensional screen printing or DTP is stainless steel and thesecond material is nickel-titanium. In another embodiment, firstmaterial is nickel-titanium and the second material is stainless steel.In other embodiments, still other materials can be used so that each endof the joining section 16 has a material composition that is compatiblewith the adjoining piece to which it will be connected or welded.

FIG. 4 illustrates one embodiment of joining section 16 formed via anelectroplating or electrodeposition process. In one embodiment, joiningsection 16 includes a first section 40 and a second section 42, suchthat first end 16 a of joining section 16 is on first section 40 andsecond end 16 b of joining section 16 is on second section 42. Each ofsections 40 and 42 are of different materials, and in one example, firstsection 40 is stainless steel and second section 42 is nickel-titanium(NiTi). In this way, first end 16 a is readily weldable to proximalsection 12 and second end 16 b is readily weldable to distal section 14,as in FIG. 1A.

In one embodiment, first section 40 is metal, such as metal alloy,stainless steel, nickel, iron, nickel-chromium alloy,nickel-chromium-iron alloy, cobalt alloy, or other similar material andproximal section 12 is of a similar material. Also in one embodiment,second section 42 is made of a relatively flexible material, such as asuper elastic or linear elastic alloy, and distal section 14 is of asimilar material. In this way, first end 16 a of first section 40 isreadily weldable to proximal section 12 and second end 16 b of secondsection 42 is readily weldable to distal section 14.

FIGS. 5A-5C illustrate one embodiment of a process for electrodepositionof joining section 16. In FIG. 5A, a mask 52 is deposited on aconductive substrate 50. Mask 52 defines an opening above conductivesubstrate 50 that is shaped to match the profile desired for joiningsection 16, in one example, cylindrical.

FIG. 5B illustrates an electrodeposition process whereby first section40 is formed within the opening of mask 52 by energizing conductivesubstrate 50. In one example, the deposition of first section 40 isachieved by putting a negative charge on conductive substrate 50 andimmersing conductive substrate 50 and mask 52 into a first electrolytesolution that contains a salt of the metal to be deposited as firstsection 40. In other words, conductive substrate 50 is made the cathodeof an electrolytic cell. The metallic ions of the salt carry a positivecharge and are thus attracted to conductive substrate 50. When theyreach the negatively charged conductive substrate 50, it provideselectrons to reduce the positively charged ions to metallic form.

In one embodiment, when first section 40 is metal, such as metal alloy,stainless steel, nickel, iron, nickel-chromium alloy,nickel-chromium-iron alloy, cobalt alloy, or other similar material, oneof these materials is dissolved in the electrolytic solution aspositively charged ions.

FIG. 5C illustrates formation of second section 42, which is built up onfirst section 40. Ions of the material that make up second section 42are then contained within a second electrolytic solution in which mask52 and conductive substrate 50 are submerged, and when conductivesubstrate 50 is energized, second section 42 is formed within mask 52against first section 40 under the force of the energized conductivesubstrate 50.

In one embodiment, when section 42 is relatively flexible material, suchas nickel-titanium (NiTi) or a super elastic or linear elastic alloy,one of these materials is dissolved in the electrolytic solution aspositively charged ions.

In another embodiment, first section 40 can be formed by other means andthen placed within mask 52 on conductive substrate 50. Then, secondsection 42 can be formed over first section 42 within mask 52 with anelectrodeposition process using conductive substrate 50 as describedabove.

FIGS. 6 and 7 illustrate other embodiments of joining section 16 formedwith an electrodeposition process. In one example, joining section 16includes first section 60 and second section 62. First and secondsections 60 and 62 are formed with an electrodeposition process asexplained above. A conductive substrate 50 and mask corresponding to theshape of first and second sections 60 and 62 are used to electrodepositone or both of first and second sections 60 and 62.

In one embodiment, first section 60 includes first extended portion 60 aand second section 62 includes second extended portion 62 a, whichoverlap along joint 65. As with above-described embodiments, eitherfirst or second section 60 or 62 can be electroplated first (orotherwise formed) and then the other section is electroplated on to thealready formed section. Joint 65 is perpendicular to first and secondends 16 a and 16 b of joining section 16. In one example, having afeature such as joint 65 running perpendicular to ends 16 a and 16 b canprovide increased holding force between first and second section 60 and62 when there is significant pulling or torque applied to proximalsection 12 and distal section 14, which are respectively coupled to ends16 a and 16 b.

In one example, joining section 16 includes first section 70 and secondsection 72. First and second sections 70 and 72 are formed with anelectrodeposition process as explained above. A conductive substrate 50and mask corresponding to the shape of first and second sections 70 and72 are used to electrodeposit one or both of first and second sections70 and 72.

In one embodiment, first section 70 includes plug portion 70 a andsecond section 72 is configured to receive plug portion 70 a. As withabove-described embodiments, either first or second section 70 or 72 canbe electroplated first (or otherwise formed) and then the other sectionis electroplated on to the already formed section. In one example,having a features such as plug 70 a formed within a receiving cavity ofsecond section 72 can provide increased holding force between first andsecond section 70 and 72 when there is significant pulling or torqueapplied to proximal section 12 and distal section 14, which arerespectively coupled to ends 16 a and 16 b.

Other configurations of joining section 16 are also possible inaccordance with other embodiments and other electro-forming methods. Inone embodiment, joining section 16 may be fabricated using LIGA orlithography and electroforming techniques. In one case, the LIGA processincludes X-ray deep lithography, electroforming and molding.

In X-ray deep lithography, a polymer layer (resist) sensitiveX-radiation is exposed to X-radiation by the shadow produced by an X-raymask, which transfers to the resist an exact image of the absorberstructures on the mask. The exposed areas are dissolved selectively bywet chemical methods. Somewhat complex or intricate configurations arepossible using lithography techniques. When these polymer structures areproduced on a metal starting layer, the structural areas exposed afterthe developing process can be filled up with various metals byelectrodeposition. Once the metal is built up, the remaining resist isremoved, and only the metal structures remain in place.

In other embodiments, EFAB® technology is used to create joining section16. EFAB® technology is a known process for forming micro-structures bystacking a set of thin metal layers, somewhat similar to rapidprototyping technologies. The EFAB® process is driven by athree-dimensional CAD of the final device. The manufacturing starts witha blank substrate and then grows the device layer-by-layer by depositingand precisely planerizing metals. In one example, two metals aredeposited (for example, one for the first section and one for the secondsection of a joining section). Somewhat complex or intricateconfigurations are possible using EFAB® processes.

FIGS. 8-11 illustrate embodiments of embodiments of joining section 16formed with an electro-forming process, such as electrodeposition, EFAB®process or a lithography process. In the embodiments of FIGS. 8-11,joining section 16 respectively includes first section 80, 90, 100, and110 and second section 82, 92, 102, and 112. First and second sections80, 90, 100, 110 and 82, 92, 102, 112 are formed with an electro-formingprocess, such as electrodeposition, EFAB® process or a lithographyprocess.

In one embodiment illustrated in FIG. 8, first section 80 includes firstand second plug portions 80 a and 80 b, and second section 82 isconfigured to receive first and second plug portions 80 a and b. In theillustration, second section 82 is ghosted and first and second plugportions 80 a and b are illustrated in dotted lines. As with first andsecond sections 80 and 82, first and second plug portions 80 a and 80 bcan be formed with electro-forming processes, such as electrodeposition,EFAB® process or a lithography process. In one example, having featuressuch as plug portions 80 a and 80 b formed within a receiving cavity ofsecond section 82 can provide increased holding force between first andsecond section 80 and 82 when there is significant pulling or torqueapplied to proximal section 12 and distal section 14, which arerespectively coupled to ends 16 a and 16 b.

In one embodiment illustrated in FIG. 9, first section 90 includes plugportion 90 a, and second section 92 is configured to receive plugportion 90 a. In the illustration, second section 92 is ghosted and plugportion 90 a is illustrated in dotted lines. As with first and secondsections 90 and 92, plug portion 90 a can be formed with electro-formingprocesses, such as electrodeposition, EFAB® process or a lithographyprocess. In one example, having a feature such as plug portion 90 aformed within a receiving cavity of second section 92 can provideincreased holding force between first and second section 90 and 92 whenthere is significant pulling or torque applied to proximal section 12and distal section 14, which are respectively coupled to ends 16 a and16 b.

In one embodiment illustrated in FIG. 10, first section 100 includesplug portion 100 a, and second section 102 is configured to receive plugportion 100 a. In the illustration, second section 102 is ghosted andplug portion 100 a is illustrated in dotted lines. As with first andsecond sections 100 and 102, plug portion 100 a can be formed withelectro-forming processes, such as electrodeposition, EFAB® process or alithography process. In one example, having a feature such as plugportion 100 a formed within a receiving cavity of second section 102 canprovide increased holding force between first and second section 100 and102 when there is significant pulling or torque applied to proximalsection 12 and distal section 14, which are respectively coupled to ends16 a and 16 b.

In one embodiment illustrated in FIG. 11, first section 110 includesfirst and second plug portions 110 a and 110 b, and second section 112is configured to receive first and second plug portions 110 a and b. Inthe illustration, second section 112 is ghosted and first and secondplug portions 110 a and b are illustrated in dotted lines. As with firstand second sections 110 and 112, first and second plug portions 110 aand 110 b can be formed with electro-forming processes, such aselectrodeposition, EFAB® process or a lithography process. In oneexample, having features such as plug portions 110 a and 110 b formedwithin a receiving cavity of second section 112 can provide increasedholding force between first and second section 110 and 112 when there issignificant pulling or torque applied to proximal section 12 and distalsection 14, which are respectively coupled to ends 16 a and 16 b.

Use of these above-described processes, such as electrodeposition,three-dimensional printing, direct typing process, LIGA, lithography orstacking processes, enables features, such as joint 65, plug 70 a, plugportions 80 a and 80 b, 90 a, 100 a, 110 a and 110 b to be produced evenwhere the wire size is quite small. For example, even where the outerdiameter of the wire is between 0.005 and about 0.02 inches, theseprocesses allow for the feature to be produced in the joining section,thereby holding the first and second materials together.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of forming a wire comprising: providing a first wire section comprising a first material; providing a second wire section comprising a second material different from the first material; forming a joining section having a first end and a second end such that the first end of the joining section comprising a material that is compatible with the first material and such that the second end of the joining section comprising a material that is compatible with the second material; and welding the first wire section to the first end of the joining section and welding the second wire section to the second end of the joining section; wherein forming the joining section comprises forming the joining section via a process selected from a group comprising electrodeposition, three-dimensional printing, direct typing process, LIGA, lithography and stacking processes.
 2. The method of claim 1, wherein the first material comprising one of stainless steel, nickel-chromium alloy, nickel-chromium-iron alloy, and cobalt alloy and wherein the second material comprising nickel-titanium.
 3. The method of claim 1, wherein the first end of the joining section comprises the first material and the second end of the joining section comprises the second material.
 4. The method of claim 1, wherein forming the joining section further comprises electrodepositing a first section of the joining section with the first material, thereby defining the first end, and electrodepositing a second section of the joining section with the second material, thereby defining the second end, and wherein electrodepositing the first and second sections further comprises forming a feature that couples the first and second sections.
 5. The method of claim 1, wherein forming the joining section further comprises three-dimensional screen printing the joining section such that the joining section comprises a gradient of materials progressing from the first material at the first end of the joining section to the second material at the second end of the joining section.
 6. The method of claim 5, wherein three-dimensional screen printing the joining section comprises printing at least three or more layers of different compositions.
 7. The method of claim 1, wherein forming the joining section further comprises using a lithography or stacking processes to build up the joining section and such that the joining section comprises a feature that couples the first and second materials.
 8. The method of claim 1, wherein forming the wire comprises forming such that the outer diameter of the wire is between 0.005 and about 0.02 inches.
 9. A method of forming a wire comprising: providing a first wire section comprising a first material; providing a second wire section comprising a second material different from the first material; forming a joining section having a first end and a second end such that the first end of the joining section comprising a material that is compatible with the first material and such that the second end of the joining section comprising a material that is compatible with the second material; coupling the first wire section to the first end of the joining section thereby defining a first interface where the first joining section material is compatible with the first material of the first wire section across the entire first interface; and coupling the second wire section to the second end of the joining section thereby defining a second interface where the second joining section material is compatible with the second material of the second wire section across the entire second interface.
 10. The method of claim 9, wherein forming the joining section comprises forming the joining section via a process selected from a group comprising electrodeposition, three-dimensional printing, direct typing process, LIGA, lithography and stacking processes.
 11. The method of claim 9, wherein the first material comprising one of stainless steel, nickel-chromium alloy, nickel-chromium-iron alloy, and cobalt alloy and wherein the second material comprising nickel-titanium.
 12. The method of claim 9, wherein the first end of the joining section comprises the first material and the second end of the joining section comprises the second material.
 13. The method of claim 9, wherein forming the joining section further comprises electrodepositing a first section of the joining section with the first material, thereby defining the first end, and electrodepositing a second section of the joining section with the second material, thereby defining the second end, and wherein electrodepositing the first and second sections further comprises forming a feature that couples the first and second sections.
 14. The method of claim 9, wherein forming the joining section further comprises three-dimensional screen printing the joining section such that the joining section comprises a gradient of materials progressing from the first material at the first end of the joining section to the second material at the second end of the joining section.
 15. The method of claim 14, wherein three-dimensional screen printing the joining section comprises printing at least three or more layers of different compositions.
 16. The method of claim 9, wherein forming the joining section further comprises using a lithography or stacking processes to build up the joining section and such that the joining section comprises a feature that couples the first and second materials.
 17. The method of claim 9, wherein forming the wire comprises forming such that the outer diameter of the wire is between 0.005 and about 0.02 inches.
 18. A method of forming a wire comprising: providing a first wire section comprising a first material; providing a second wire section comprising a second material different from the first material; forming a joining section having a first end and a second end such that the first end of the joining section comprising a material that is compatible with the first material and such that the second end of the joining section comprising a material that is compatible with the second material; characterized in that forming the joining section comprises forming a first section of the joining section in a mask via an electroplating process, the first section defining the first end, and forming the second section of the joining section in the mask and on the first section via a further electroplating process, the second section defining the second end. 